A freeze fracture survey of a prostate gland is made for the first time. Our objectives include: 1) the preparation of a description of cells in the prostate gland, 2) their changes under different conditions of fixation, 3) the observation of membrane events related to secretory processes, 4) the elucidation of temperature and fixation related structural alterations of the membranes of the endoplasmic reticulum and nuclear envelope and 5) the study of rapid changes of the functional complex of the epithelial cells under controlled experimental conditions.